Transport refrigeration systems commonly employ the hot gas discharge gas from a refrigerant compressor during a heating cycle initiated to hold a predetermined set point temperature in a served space, directing the hot gas to the evaporator during such heating cycle instead of to a condenser. A similar operation takes place during a defrost cycle initiated to melt frost which may have accumulated on the evaporator.
The lower the ambient, the greater the thermal capacity requirement during a heating cycle. Refrigeration systems are designed in an attempt to balance the heat absorbed by an evaporator and the heat rejected by a condenser, as the efficiency is determined by the poorest component. Thus, some systems route radiator coolant from an engine to a heat exchanger wrapped around the accumulator, to add heat to the system. During cold ambients, however, when heat is needed the most, the amount of heat available from radiator, coolant drops and hot gas heating and defrosting suffer.
It is an object of the present invention to enhance hot gas heating and hot gas defrosting cycles of a transport refrigeration system, while reducing dependency upon how much heat is absorbed in an accumulator tank.